Screening and production of a potent extracellular Arthrobacter creatinolyticus urease for determination of heavy metal ions

This paper describes the isolation of a potent extracellular urease producing microorganism, identified by 16S rRNA as Arthrobacter creatinolyticus MTCC 5604 and its medium optimization by classical one-factor-at-a-time method and central composite rotatable design (CCRD), a tool of response surface methodology (RSM). An optimal activity of 9.0 U ml−1 was obtained by classical method and statistical optimization of the medium resulted in an activity of 17.35 U ml−1 at 48 h and 30 °C. This activity was 4.91 times greater than the initial activity (3.53 U ml−1) from the basal medium and the enzyme showed maximum activity at pH 8.0 and 60 °C and was stable at pH 7.0–9.0 and temperatures up to 50 °C. Furthermore, the enzyme was assessed for its activity reduction by determining the inhibitory concentration (IC50) of heavy metal ions and the inhibition of urease was in the order of Cu(II) > Cd(II) > Zn(II) > Ni(II). Urease was highly sensitive to Cu(II) and its inhibition was 94% and 100% in model solutions containing a mixture of Cu(II) with heavy metal ions Cd(II) and Zn(II), respectively. The results of these studies suggested that the enzyme could be utilized as sensors to determine the levels of Cu(II) ions in industrial effluents, contaminated soil and ground water.